Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: Prev 1 2 3 [4]   Go Down
  Print  
Author Topic: Want t buy AMP but I want to hear the difference  (Read 10715 times)
N9DG
Member

Posts: 365




Ignore
« Reply #45 on: May 01, 2009, 06:22:59 AM »

"::Interesting reply, but this can't be accurate, either. S-9 = 50mV? I doubt it. Probably 50uV."

Yes, the "mV" vs. "microvolts" was presented incorrectly, it is 50 microvolts (into 50 ohms).


"S units cannot be 6 dBm, but they could be 6 dB. dBm is an absolute value, while dB is a ratio. There's a big difference."

Correct. But the take away point is that if you feed it a signal at -73 dBm it will read S-9, then if you dial back the signal generator to -79 dBm it will read S-8, and you can keep doing this in 6 dB steps right on down to the Flex's noise floor, or up to 40 dB over S-9 and it will track extremely close to the 6 dB per S unit "standard". I can't think of any other amateur market radio that can do this.
Logged
N9DG
Member

Posts: 365




Ignore
« Reply #46 on: May 01, 2009, 06:45:54 AM »

"... or up to 40 dB over S-9 ..."

I should have stated that as: "or up to the upper limit of the A to D". Which is quite a bit more than 40 db over S-9. I just don't remember exactly what that upper limit actually is off hand.
Logged
WB2WIK
Member

Posts: 21837




Ignore
« Reply #47 on: May 01, 2009, 09:21:15 AM »

RE: Want t buy AMP but I want to hear the difference       Reply
by N9DG on May 1, 2009    Mail this to a friend!


Correct. But the take away point is that if you feed it a signal at -73 dBm it will read S-9, then if you dial back the signal generator to -79 dBm it will read S-8, and you can keep doing this in 6 dB steps right on down to the Flex's noise floor, or up to 40 dB over S-9 and it will track extremely close to the 6 dB per S unit "standard". I can't think of any other amateur market radio that can do this.<

::Actually, my 30 year-old Drake TR-7 can do that, with its panel analog meter (within resolution accuracy of the movement itself).

I just tried it last night (again): S9 at 14 MHz = 47.4 uV; S8 = 41 uV; S7 = 34.6 uV; S6 = 29uV; S5 = 23.2 uV; etc.  10 dB/S9 = 150 uV; 20 dB/S9 = 484 uV; 30 dB/S9 = 1.6 mV; 40 dB/S9 = 5.04 mV.  That's all within a few percent of dead-on perfect, and about as close as the meter needle can resolve.  30 year old technology.

They didn't use any level reference and comparator, just very wide dynamic range AGC.

WB2WIK/6
Logged
K1BXI
Member

Posts: 821




Ignore
« Reply #48 on: May 01, 2009, 10:44:04 AM »

Anyone remember those Hallicrafters receivers of the mid 50's, like the SX-99 etc? Some of them had a scale to 100 dB over S9. I wonder if that was a marketing ploy because maybe they sold more than the other guy's that only went to 60 over.

I always loved to get a report that I was 90 dB over 9 with my DX-100 on 75 meters.

Logged
WB9JOX
Member

Posts: 106




Ignore
« Reply #49 on: May 02, 2009, 07:32:10 AM »

Hi,the most you will see is about 2-3 s unit increase with 1kw out put for the most part.The first 500 watts makes the difference.Like the other ham said talk to some one on the air and hear signal with 100 watts and then with amp on.73
Logged
KH6AQ
Member

Posts: 7974




Ignore
« Reply #50 on: May 03, 2009, 08:15:18 AM »

The original question was posed so that a decision could be made between several amps.

Bottom line: More power will give a better signal and that means more fun. If you have the money buy the bigger amp.

My personal experience is that adding a 500 watt amp to my 100 watt radio has made a HUGE difference in how enjoyable CW is. I work DX running a very modest antenna (ground mounted screwdriver) and with 500 watts I can get through pile-ups and work plenty of DX on 80 and 40 meters from Utah.
Logged
AD5X
Member

Posts: 1626




Ignore
« Reply #51 on: May 03, 2009, 09:17:26 AM »

I'm also a virtually 100% cw operator, and I agree that going from 100 watts to 500-600 watts makes a huge difference when I need it.

But now that we have these nice SDR radios like the K3 and Flex 3K/5K, maybe it is time to change the RST system since we can read out the incoming power directly in dBm.  So maybe a signal report should be "5 -73dBm 9" now, instead of "599".  Of course this takes a little longer to say, especially on cw. :-)

Phil - AD5X
Logged
AE5I
Member

Posts: 124




Ignore
« Reply #52 on: May 30, 2009, 12:59:59 AM »

K8AC wrote:
" I submit there are NO current rigs that are calibrated to 6dB per S-meter unit"

Actually, there's at least one:  the Ten-Tec Omni-VII.  I measured one over most
of the S-meter's range and it was within +/- 1 db of that standard.

The old Collins and Drake rigs were calibrated well too.

Agreed on lots of current rigs though:  their meter calibration is all
over the place.  Not necessarily 3 db per unit, but 1 at one point, 2 at another
point and 5 somewhere else...  Not useful for much other than giving
signal reports that will make the other op happy!  ;-)

73

Tom AE5I
Logged
KB1LKR
Member

Posts: 1897




Ignore
« Reply #53 on: May 31, 2009, 11:37:10 AM »

WA9UAA was saying: "...a relative S/N reading being used rather than an 'absolute' value..."

In an RST report this numeric value of S/N would lead to a 1-5 R readability ranking vs. a 1-9 S signal strength ranking, though, as noted, really the more important of the two, and handy to attempt to quantify vs. just qualifying Readability mentally, though there should also be a mental component for a phone signal over compressed/processed or with excessive room echo or excess background noise, or CW w/ bad chirp or uneven dot dash timing/spacing, etc. could still be difficult to read even if S/N was very good.

Signal strength, is a different thing than signal readability, though the two can go hand in hand, ideally on a calibrated meter (and I can see the merit of using units dBm (or uV into 50 ohms even) over the Collins standard S unit (50uV into 50 ohms or -73dBm = S9 and -6dB per S unit; so S5 = -97dBm, S1 = -109dBm, etc) on an SDR radio (or a conventional radio w/ a custom meter even (interesting HB project?) -- though the latter may be more familiar (and perhaps easier to convert to a 0-9 relative Signal ranking from a relative meter reading) -- is still  going to be dependent on the receive antenna (and potentially beam heading) as well as propagation conditions along the path and the transmitter/antenna system's ERP on the path heading (azimuth & elevation).

In some respects it's a case of changes in technology that now permit easier accurate reading of signal power or voltage into a known load (and potentially a S/N measurement in addition to initially relative, qualitative units/scales (1-5, 1-9) and later a proposed, standard Strength scale (Collins Radio). Interesting times & interesting tangent to the original question of "how's a amplifier going to sound?".

So, (even farther off original topic) for reception of (a strong, clearly readable) CW sent in A2A vs. A1A would you still report 599 or would it technically be 598 (as there is/are modulation tone(s) by design, (but not AC line ripple) on the signal?
Logged
Pages: Prev 1 2 3 [4]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!